Figure 4.

Estradiol (10 nM) or S1P (200 nM) promotes osteoblast differentiation. (A) (i) Alkaline phosphatase activity after treatment for 3 weeks is shown in whole 9 cm² cultures. (ii) Cells photographed after staining with ALP at 20× magnification without phase. (iii) At low power, 10×, in phase, the dense developing tissue and collagen are revealed. (iv) Cells photographed after staining with alizarin red at 20× magnification. (B) ALP activity quantified by densitometry analysis and normalized to cell number. Both estradiol and S1P increase ALP activity compared with the control. Results are mean ± SEM, n = 4. **p < 0.01 versus control.